Different types of fuels expand and transfer energy at higher rates than others.

 

Here's a slightly related question:

From what I understand the ECU has a high and low octane map, and which map you're in is based on knock history. Since knock is a function of octane, does anyone know roughly what base octane you need to stay out of the low octane map?

Here in Nebraskee, the best we get is BP 92, but I think that's still keeping me in the low octane map. I put 4 gallons of GT 100 in the tank w/ the BP 92, and now that half that has run out I think the ECU has figured out it's not running on pee water. I'd like to put in the minimum amount of GT 100, since any more than needed to keep me out of the low octane map is wasted $.

 

Makes good sense, a dim bulb has brightend

 

(quote= Samuel Jackson)

Correct-a-mundo Mother ##ucker

(/ Samuel Jackson)

 

im just going to guess but, Shaft?

 

I figured this thread wouldnt be around for long but im glad everyone chimed in and continued to ask questions. Learned a few things

 

I did too.

 

Off the topic but you should just go and get and alky kit and then have your car tuned for it. cheaper I think in the long run and you get good gains w/alky.

 

Exactly why companies like VP, which specialize in this stuff, make lots of different fuels that have nearly the same octane rating. And that doesn't count custom specialty fuels.

The point I was trying to make about automatically running rich on "race gas" is that as a blanket statement it's false. Remember, pump gas is made the cheapest way possible to meet certain functional specs. Therefore its "hard" physical properties can be all over the map. Any particular blend of race gas is formulated to be consistent but there are a lot of blends, so to compare pump gas to race gas doesn't really pin things down much.

Dave

 

Pulp fiction actually.

 

^damn!!


guess you've seen that once or twice!!

 

You don't really think a $200 WB is always accurate to 0.1 AFR do you? They're a heck of an instrument and you don't want to tune without one, but that claim, which all the vendors make, has to be taken with a grain of salt. Note that Innovate's product doesn't trust the Bosch calibration resistor -- that's why you have to do the free air calibration -- Allmendinger didn't consider it accurate enough.

Anyway, I'm not saying that race gas would never make you run richer than pump gas, just that it's not always true. And actually I'd say most times it isn't. I used to be an analytical chemist, I measured stuff to part per billion levels for a living, there's more to a measurement than just reading what's on the display. In this case you could probably get a good idea of whether race gas makes your AFR richer by running in closed loop (idle will do) and watching your short-term fuel trim while switching between pump and race gas a couple times.

Dave

 

There's absolutely no guarantee that the fuel you get at the pump is top-notch, especially if you're buying it from some shmoe's gas pump down the street that charges a lot less than an Exxon station. All you're really buying when getting race gas is a better petroleum product so you're less likely to knock due to abberations in the fuel that aren't filtered out. Less knock is an improvement.

But as others have said, if you're not tuned for leaded race gas the stock tune on your car is not taking full advantage of the potential energy within the gas.

It's not worth dumping 116 in your car without a tune for it based purely on the cost per improvement perspective... but in a very small (technical) way it is better. Just not enough to really matter.

 

So here is a crazy question while on the gas subject. Do you all believe in going to specific gas stations. For example I am a Shell gasoline ***** for pump gas. But I have been told it doesnt really matter too much where you fill up. But Shell has a "cleaning system", and so does or did Chevron. I heard Chevrons gas wasnt all that good for cars.

Any ideas?

 

Actually there is an octane booster out there that does work. My friend was involved in its initial introduction and testing. The stuff works great.

We used it in my friends 330whp WRX a few months back. While running a 100 octane fuel map, we used the additive which was added to 93 octane fuel and not only did the car run perfectly with no pinging/det, etc.... it pulled the same HP on the dyno that the car did with 100 octane VP race fuel.


My Audi A4 which ran 23psi of boost tended to ping with 91 octane California crap fuel but while running this additive even on 87 octane fuel.... not a single issue with pinging and ran strong as ever.

http://www.americancleanenergysystems.com/aces4.html

edit: Btw... this octane booster has been used for quite a while by the US Military and was recently declassified. It was initially designed to make up for the low octane and poor fuel quality in countries around the world where US troops have been stationed or fighting in wars.